Cooking Appliance

ABSTRACT

A cooking appliance, in particular, a cooking appliance which is mounted in an elevated manner. Said cooking appliance comprises at least one muffle which is defined by a cooking chamber and which comprises a muffle opening, a door which is used to close the muffle opening and a drive motor which is used to displace the door. The drive motor is equipped with a self-locking transmission.

The present invention relates to a cooking appliance, especially a high-level cooking appliance with a muffle enclosing at least one cooking chamber, with a muffle opening, a door which is used to close the muffle opening and a drive motor which is used to move the door.

Locking catches are already known as a method of locking for cooking appliances with motor-driven doors. The disadvantage of these locking catches is the space that they require.

The object of the present invention is to provide a cooking appliance with a facility for secure and compact locking of the door.

The present object is achieved by the cooking appliance with the features of claim 1. Advantageous embodiments can be found individually or in combination in the subclaims.

To this end the cooking appliance, especially a high-level cooking appliance but also a cooking appliance with a motorized oven carriage, is equipped with a drive motor and with a self-locking transmission. The self-locking transmission enables, in the closed state of the door, a mechanical pulling open of the door against the motor to be rendered difficult to the extent where the opening of the door can be safely prevented.

Advantageously the self-locking transmission is a worm transmission.

It has proved useful, especially for a high-level cooking appliance, for the self-locking transmission to have a transmission ratio ranging from 30:1 to 60:1, especially ranging from 40:1 to 30:1, specifically 45:1. The base door of a high-level cooking appliance would not move with a transmission ratio of 45:1, even with a load of over 20 kg.

It is advantageous for self-locking for drive motor to be short circuited in the closed state of the door since the opening force must then be applied against the self-induction of the motor.

The invention will be described in more detail below on the basis of the exemplary embodiments shown in the enclosed figures. The figures show:

FIG. 1 a perspective view of a high-level cooking appliance mounted on a wall with its base door lowered down;

FIG. 2 a perspective view of the high-level cooking appliance with its base door closed;

FIG. 3 a perspective view of a housing of the high-level cooking appliance without the base door;

FIG. 4 a schematic side view in cross-section along the line I-I from FIG. 1 of the high-level cooking appliance mounted on the wall, with its base door lowered down;

FIG. 5 a further embodiment of a high-level cooking appliance viewed from the front;

FIG. 6 a front view of the embodiment from FIG. 5 in the closed state with a more precise description of the location of individual housing elements;

FIG. 7 a view from above in cross-section of the embodiment from FIG. 6;

FIG. 8 parts of the drive apparatus for a more precise description;

FIG. 9 in a side view similar to that shown in FIG. 4 of a further embodiment of the high-level cooking appliance;

FIG. 10 the embodiment of the cooking appliance according to FIG. 9 in a cross-sectional front view;

FIG. 11 a section from FIG. 10 in greater detail;

FIG. 12 a further embodiment of the high-level cooking appliance with emergency opening arrangement in a view similar to that shown in FIG. 7.

For better presentation of the individual elements the figures are not drawn to scale.

FIG. 1 shows a high-level cooking appliance with a housing 1. The rear of the housing 1 is mounted on a wall 2 in the manner of a wall-mounted cupboard. A cooking chamber 3, which can be checked via a viewing window 4 set into the front of the housing 1, is defined in the housing 1. It can be seen from FIG. 4 that the cooking chamber 3 is delimited by a muffle 5, which is provided by a heat-insulating jacket not shown in the figure, and that the muffle 5 features a muffle opening 6 on the floor side. The muffle opening 6 can be closed by a base door 7. FIG. 1 shows the base door 7 in a lowered position, in which its lower side is in contact with a work surface 8 of a kitchen unit. To close off the cooking chamber 3, the base door 7 should be moved into the position shown in FIG. 2 known as the “zero position”. To adjust the position of the base door 7 the high-level cooking appliance has a drive apparatus 9, 10. The drive apparatus 9, 10 has a drive motor 9, shown in FIGS. 1, 2 and 4 by the dashed outline, which is arranged between the muffle 5 and an outer wall of the housing 1. The drive motor 9 is arranged in the area of the rear of the housing 1 and, as shown in FIG. 1 or 4, is actively connected to a pair of lifting elements 10, which are connected to the base door 7. In this case, as depicted in the schematic side view shown in FIG. 4, each lifting element 10 is designed as an L-shaped support, of which the vertical arm extends downwards from the housing-side drive motor 9. To position the base door 7 the drive motor 9 can be actuated with the aid of a control panel 12 and a control switch 13 which is arranged as shown in FIG. 1 and 2 on the front of the base door 7. As shown in FIG. 4, the control circuit 13 is located behind the control panel 12 within the base door 7. The control circuit 13, which consists here of a number of circuit boards in different locations and performing different functions, and communicating via a central communication bus, represents a central control unit for appliance operation and controls and/or regulates for example heating up, movement of the base door 3, implementation of operator input, an illumination, anti-trapping measures, timing of the heating elements 16, 17, 18, 22 and much more besides.

It can be seen from FIG. 1 that an upper side of the base door 7 features a cooking zone 15. Almost the entire surface of the cooking zone 15 is taken up by heating elements 16, 17, 18 which are shown as dashed outlines in FIG. 1. In FIG. 1 the heating elements 16, 17 are two separate different-sized hotplate elements, whereas heating element 18 is a radiant heating element provided between the two hotplate heating elements 16, 17 which practically surrounds the hotplate heating elements 16, 17. Hotplate heating elements 16, 17 define associated heating zones or heating areas for the user; Hotplate heating elements 16, 17, together with radiant heating element 18, define a bottom heat zone. The zones can be indicated by a suitable decor on the surface. Heating elements 16, 17, 18 can each be activated via the control circuit 13.

In the exemplary embodiment shown the heating elements 16, 17, 18 are embodied as radiant heating elements which are covered by a glass ceramic plate 19. The glass ceramic plate 19 has approximately the same dimensions as the upper side of the base door 7. The glass ceramic plate 19 is also equipped with installation openings (not shown), through which sockets for holding holder elements 20 for pot supports 21 extend, as shown in FIG. 4. Instead of a glass ceramic plate 19 other—preferably fast-response—covers can also be used, e.g. a thin metal sheet.

With the aid of a control knob provided in the control panel 12 the high-level cooking appliance can be switched to a hotplate or a bottom heat operating mode, which will be explained below.

In the hotplate operating mode the hotplate heating elements 16, 17 can be activated individually by means of control elements 11, which are provided in the control panel 12, via the control circuit 13, whereas the radiant heating element 18 remains inoperative. The hotplate operating mode can be executed with the base door 7 lowered as shown in FIG. 1. It can however also be operated in a closed cooking space 3 with a raised base door 7 in an energy saving function.

In the bottom heat operating mode, not only the hotplate heating elements 16, 17 but also the radiant heating element 18 is activated by the control circuit 13.

In order to achieve the most even possible browning profile of the food being cooked during bottom heat operation, it is of decisive importance for the cooking zone 15 providing the bottom heat to have an even distribution of the heat power output over the surface of the cooking zone 15, although the heating elements 16, 17, 18 have different rated outputs. Preferably the heating elements 16, 17, 18 are thus not switched on permanently by the control circuit 13 but the power supply to the heating elements 16, 17, 18 is timed. In this case the different levels of rated heating power of the heating elements 16, 17, 18 are reduced so that the heating elements 16, 17, 18 create an even distribution of the heating power output over the surface of the cooking zone 15.

FIG. 3 shows a schematic diagram of the position of an air recirculation bowl 23 with a recirculation motor and an assigned annular heating element, e.g. for creating hot recirculated air in hot air operation. The air recirculation bowl 23 open to the cooking chamber 3 is typically separated from the latter by an impact wall (not shown). In addition an overhead heating element 22 mounted on an upper side of the muffle 5 is provided which can be embodied with a single circuit or with multiple circuits, e.g. with an inner and an outer ring. Through the control circuit 13 the different operating modes such as overhead heating, hot air heating or rapid heating-up mode can also be set for example by the corresponding switching on and switching off of the heating output of the heating element 16, 17, 18, 22, if necessary with activation of the fan 23. The heat power can be set by suitable timing. In addition the cooking zone 15 can also be of a different design, e.g. with or without an extended cooking zone, as a pure single or multi-circuit heat retention zone without cooking areas and so forth. The housing 1 has a seal 24 against the base door 7.

The control panel 12 is primarily arranged on the front of the base door 7. Other alternative arrangements are also conceivable, e.g. on the front of the housing 1, divided up into different subpanels and/or partly on side surfaces of the cooking appliance. Further embodiments are possible. The design of the control elements 11 is not restricted and can for example include control knobs, rocker switches, pushbuttons and foil switches which include display elements 14, e.g. LED, LCD and/or touchscreen displays.

A front view of a high-level cooking appliance is shown schematically and not true-to-scale in FIG. 5, in which the base door 7 is open and in contact with the work surface 8. The closed state is shown by a dotted outline.

In this embodiment there are two movement control panels 25 on the front side of the permanently attached housing 1. Each movement control panel includes two press buttons, namely an upper CLOSED button 25 a for a base door 7 moving upwards in the closing direction and a lower OPEN button 25 b for a base door 7 moving downwards in the opening direction. With no automatic mode the base door 7 only moves upwards with a continuous simultaneous pressure on the CLOSE buttons 25 a of the two movement control panels 25; the base door 7 also only moves downwards, where possible, with a continuous simultaneous pressure on the OPEN buttons 25 b of the two movement control panels (manual operation). Since in manual operation the user has to take greater care during operation and in addition both hands are used for this operation, anti-trapping protection is then only optional. In an alternate embodiment the movement control panels 26 are accommodated on opposite outer sides of the housing 1 with the corresponding CLOSE buttons 26 a and OPEN buttons 26 b, as shown by the dotted outline.

The control circuit 13 indicated by a dashed outline which is located inside the base door behind the control panel 1, switches the drive motor 9 so that the base door 7 starts to move smoothly, i.e. not abruptly by simply starting the drive motor 9, but by using a defined ramp.

The control circuit 13 in this exemplary embodiment includes a memory unit 27 for storing at least one target or movement position P0, P1, P2, PZ of the base door 7, preferably with volatile memory chips, e.g. DRAMs. If a target position P0, P1, P2, PZ is stored, the base door can move after actuation of one of the buttons 25 a, 25 b or 26 a, 26 b on the movement control panels 25 or 26 in the direction set automatically until such time as the next target position is reached or one of the buttons 25 a, 25 b or. 26 a, 26 b is actuated once more (automatic mode). In this exemplary embodiment the lowest target position PZ corresponds to the maximum opening, the (zero) position P0 to the closed state, and P1 and P2 to freely-selectable intermediate positions. Once the last target position for a direction has been reached in manual operation the door must be moved beyond this position if this is possible (meaning that the last end positions do not correspond to a maximum opened or the closed end state). In a similar manner, when no target position is stored for a direction—which for example would be the case for an upwards movement into the closed position, if only PZ is stored, but not P0, P1, P2—the door must be moved in this direction in manual mode. If no target position is stored, e.g. with a new installation or after a power disconnection, no automatic mode is possible. If the base door 7 is moved in automatic mode an anti-trapping protection is preferably activated.

Automatic mode and manual mode are not mutually exclusive: Continuous pressure on the movement control panel or panels 25, 26 causes the base door 7 to move in manual operation even if a target position were able to be moved to in this direction. In this case for example a maximum actuation time of the movement control panels 25 or 26 or the associated buttons 25 a, 25 b or 26 a, 26 b respectively can be defined for activation of automatic mode, e.g. 0.4 seconds.

A target position P0, P1, P2, PZ can be any position of the base door 7 between and including the zero position P0 and the maximum opening position PZ. The maximum stored opening position PZ does not however have to be the position at which the door is resting on the work surface 8. The target position P0, P1, P2, PZ can be stored with the base door 7 at the desired target position P0, P1, P2, PZ, by for example actuating an actuation button 28 in the control panel 12 for a number seconds (e.g. a period of two seconds). Existing optical and/or acoustic signal generators which output appropriate signals after a target position has been stored are omitted from the diagram to improve its clarity. Moving the door to the desired target position P0, P1, P2, PZ to be set is undertaken for example by—in this exemplary embodiment—two-handed operation of the movement control panels 25 or 26 and manual movement to this position.

Just one, or as shown in this exemplary embodiment, a number of target positions P0, P1, P2, PZ, can be stored in the memory unit 27. With a number of target positions P0, P1, P2, PZ, these positions can be moved to in turn by actuating the corresponding movement buttons 25 a, 25 b or 26 a, 26 b. The number of target positions P0, P1, P2, PZ enables the high-level cooking appliance to be adapted conveniently to the desired operating height of a number of users. The target position(s) are advantageously able to be deleted and/or overwritten. In one embodiment for example only one target position is able to be stored in the open state whereas the zero position P0 is automatically detected and the door is able to be moved to this position automatically. Alternately the zero position P0 must be stored to enable the door to be moved there automatically.

It is especially advantageous for ergonomic use if the target positions or a target position P1, P2, PZ opens the base door 7 at least appr. 400 mm to appr. 540 mm for (i.e. P1−P0, P2−P0, PZ−P0≧40 cm to 54 cm). With this opening dimension the food supports 21 can be easily placed into their holder elements 20. In this case it is useful for the viewing window to be mounted at about the eye level of the user or slightly below, e.g. using a template which indicates the dimensions of the cooking appliance.

Shown in the drawing is an existing uninterruptible power supply for bridging a power failure of around 1 to 3 seconds, preferably of around 1.5 seconds.

The drive motor 9 from FIG. 1 has at least one sensor unit 31, 32 on a motor shaft 30, if nec. arranged in front of or behind a transmission, in order to measure a movement path or a position and/or a speed of the base door 7. The sensor unit can for example also include one or more induction, Hall, opto, OFW sensors and so forth. In this case, for simple measurement of the path and speed two (part) Hall elements offset by 180°—i.e. opposite each other—are accommodated on the motor shaft 30, and a Hall measurement recorder 32 is fixed permanently at a distance in this area of the motor shaft. if a Hall element 31 then moves past the measurement recorder 32 as the motor shaft 30 rotates, measurement or sensor signal is created which is a good approximation of a digital signal. With (not necessarily) two Hall elements, two signals are thus output for one rotation of the motor shaft 30. By evaluating the timing of the signals, e.g. their time difference, the speed vL of the base door 7 can be determined, for example using comparison tables or a conversion in real time in the control circuit 13. By addition or subtraction of the measurement signals a movement path or a position of the base door 7 can be determined.

A speed regulator can for example implement the speed via a PWM-controlled power semiconductor.

For determining the zero position the path measurement is automatically newly synchronized in the zero position P0 of the base door 7 for each movement to this position, so that for example an error in a sensor signal output or detection does not have any effect.

The drive motor 9 can be operated by actuating the two movement control panels 25 or 26 even with the main switch 29 switched off.

Instead of two separate switches per movement panel 25, 26, a single switch per movement panel is also possible, e.g. a rocker switch with a neutral position which only switches under pressure. Other forms are also possible. The type and arrangement of the control elements 28, 29 of the control panel 12 is also not restricted.

The arrangement and subdivision of the control circuit 13 in this case is flexible and not restricted, meaning that it can also consist of a number of circuit boards e.g. a display circuit board, a control circuit board and a lift circuit board which are at separate locations.

A 4 mm opening dimension can be detected by end switches 33, which on actuation deactivate an anti-trapping protection.

The high-level cooking appliance can also be embodied without a memory unit 27, with no automatic mode then being possible. This can be useful for increased operator safety, e.g. for anti-trapping protection.

FIG. 6 shows a schematic diagram (not true to scale) viewed from the front to illustrate the position of individual elements of the housing 1 in the closed state, in which the base door 7 is against the muffle 5 to close it and in doing so also closes off the housing 1 optically. The housing 1 consists of an (inner) housing body 34 (shown as a dashed line) and a housing cover or panel 35, which surround the housing 34 at least at the front and the side. The intermediate space 36 between housing body 34 and housing cover 35 is embodied so that the cooling air can flow at least partly through it. For this purpose lower ventilation openings 37, e.g. ventilation slots, are provided in the housing cover 35 which are mounted more deeply than the upper surface 38 of the housing body 34, preferably in a region in the vicinity of the muffle opening or of the lift floor 7. The ventilation openings 37 are made here on the underside of the housing cover 35; but can also for example be present on its sides. One or more corresponding upper ventilation openings 39, e.g. an exhaust slot, a located in the upper part of the housing cover 35, specifically in its roof. This enables a flow of air consisting of cooling air to be built up through the intermediate space 36, typically from bottom to top of which is then discharged through the roof.

The muffle (shown by a dotted outline) is mounted in the housing body 34, with the associated intermediate space 40 being clad with insulation material except for its front side. The muffle 5 is conversely embodied in a U-shape. To allow the operator to look into the cooking chamber 3 a number of viewing windows 4 are present, namely a first (inner) viewing window 41 directly covering the muffle 5 (shown by a dotted outline) which thus at least partly represents one wall of the muffle 5, furthermore a second (middle) viewing window 42 held by the housing body 34 (also shown by a dotted outline) and a third (outer) viewing window 43 in the housing cover 35.

Optionally further intermediate windows can be inserted (not shown) which are preferably attached to the housing body 34, or fewer viewing windows 4 can be present e.g. only the inner and the outer viewing window 41, 43. The ventilation slots 37, 39 can also be installed in another arrangement and form.

FIG. 7 shows, in a view onto the housing I from above, according to the section plane III-III from FIG. 6 (i.e. without upper housing wall) a more detailed, not true-to-scale view of the inside of the housing with different elements arranged within it. This provides a good view of the spaces 36 between housing body 34 and housing cover 35, namely the side spaces 44, the front space 45 and the rear space 46. Because of the three viewing windows 41, 42, 43 the front space 45 is divided up vertically into a first front space 45 a between middle viewing window 42 and outer viewing window 43 and a second front space 45 b between middle viewing window 42 and inner viewing window 41. Naturally the spaces do not have to be empty but can feature different elements, such as lifting elements 10, brackets, breakthroughs, insulation, air guide elements such as ventilation baffles, screws, struts etc., with not every space 36 also having to allow a significant cooling air stream.

The following are especially mounted on the housing body 34: Electrical or electronic modules 47 such as the control circuit 13, a drive apparatus 48 and a fan device 49.

The fan device 49 comprises at least one fan, which in this embodiment is precisely one fan which sucks in air by means of two inlet openings from two directions. A two-section fan is advantageously used here in which additionally the exhaust air is output at least essentially unmixed. Especially suitable is the double radial fan 50 shown here which has two inlet openings lying opposite one another and discharges the induced air to the side. In this case the two induced air flows are essentially output sideways in parallel to each other.

In the form of construction shown here an inlet opening of the double radial fan 50 is connected to an induction channel 51 which covers the front space 45 at least partly from above and thereby sucks in air during operation from below out of the lower ventilation openings 37 through the front space 45. This means that the front space 45 is cooled for improved operator safety, since because of its viewing windows 4, 41-43 this space provides lower heat insulation.

The other (rear) induction opening of the double radial fan 50 is open. Air is sucked in through this opening especially from the side spaces 44 and the rear space 46 and flows over the upper surface 38 to the fan 50. This means that the components arranged on the upper surface also have a flow of air around them which cools them. This is especially advantageous for the electronics module 47.

The exhaust air of the fan 50 flows through an exhaust air duct 52 to an upper air outlet 53, which blows the air out through the ventilation opening(s) 39 from FIG. 6.

The drive apparatus 48 comprises a motor 9 attached centrally on the surface 38 of the housing body 34 on which a guide housing 54 rests. Two guide channels (not shown) run through the guide housing 54. The guide housing 54 has a circular cutout for introducing a pinion 55 of the motor 9. The guide channels lead upwards past the sides of the cutout, so that ropes, cables etc. located in the guide channels are made to engage with the pinion 55. Attached to the outer openings of the guide channels, i.e. at four openings here, are guide tubes 56, which, together with the guide channels, form continuous cable channels. The guide tubes 56 extend in this embodiment from the guide housing 54 to the edge of the upper surface 38 into an area above the lifting elements 10 and onwards over the edge down into the lifting elements 10.

Running in each of the two cable channels is a hoisting cable as drive cable (not shown). The hoisting cable has a bendable metal core and is wire-wrapped. One end of each hoisting cable is fixed to the base door 7, the other is free. Since the two hoisting cables engage with the pinion 55 on opposite sides, they are displaced linearly by the rotation of the pinion 55 in opposite directions. The hoisting cable drive can for example be obtained from WEBASTO in Germany.

The guide tubes 56 are elastically deformable, e.g. formed from die-cast aluminum. At least one load-bearing guide tube 56 (i.e. a guide tube 56 which guides a section of a hoisting cable which is permanently connected directly or indirectly to the base door 7; meaning that there is a load on this section of the hoisting cable) rest on a support 57 with the support force depending on the size of the load at the hoisting cable. In this embodiment such a support 57 is provided for each load-bearing guide tube 56. The supports 57 are essentially located at the edge of the upper surface 38 of the housing body 34, so that the length—of the “arm”—of the guide tube 56 able to be deflected under load is large. This means that the load dependency of the essentially perpendicular force exerted by the respective guide tube 56 on the support 57 is as large as possible. The support force depends for example on the loading of the base door 7 or its placement on a support surface or an object. By measuring the support force for example a protection against overloading of the base door 7 or an anti-trapping protection can be implemented.

The length of the guide tubes 56 is at the discretion of the designer and can be comparatively short or can extend as far as the attachment of the hoisting cable to the base door 7 (in the closed state).

To use the support of the hoisting cables for load measurement the use of a guide tube 56, although advantageous for reasons of smooth movement and friction, is however not absolutely necessary. It is also possible to route the hoisting cables—or cable or rope in general—freely over suitably positioned supports (reaching over the edge of the surface). The supports are then expediently embodied accordingly, e.g. made from a suitably hard and/or slippery material, surface-treated or surface coated.

The use of a hoisting cable drive is also not mandatory, but is advantageous because of the simple construction and assembly as well the precise movement. Alternate drives include those with a driven side drum etc. for example.

To describe the drive principle more precisely, FIG. 8 shows a view from above of the guide housing 54 with guide tubes 56 joined to it, which form two separate guide channels, namely—in this diagram—an upper and a lower guide channel. Running in each of the guide channels 54, 56 is a hoisting cable 58, typically of around one meter in length. The guide channels route the hoisting cables 58 to a cutout in the guide housing 54, through which a toothed wheel or pinion 55 driven by the drive motor projects. The teeth of the pinion 55 engage with the winding wire of the respective hoisting cable 58, which, as far as the pinion 55 is concerned, forms a type of linear sequence of teeth.

When the pinion 55 is turned by the drive motor—in the clockwise direction indicated by the solid arrows here—the upper hoisting cable 58 is displaced linearly from left to right and the lower cable 58 is moved by the same amount from right to left, as indicated by the dashed arrows.

Since the hoisting cables 58 are permanently engaged with the pinion 55 and are thereby permanently coupled to the drive motor, an effective locking of the base door in the opening direction can also be achieved, e.g. to protect against the door being opened when the cooking chamber is hot, for example during pyrolysis, or when the child lock is switched on. Previously a mechanical locking has been used for locking which, depending on specific parameters such as a threshold value temperature etc., typically closes the door by means of a locking latch. However this type of locking can be dispensed with if the drive motor according to reference character 9 from FIG. 7 for example drives the pinion 55 via a self-locking drive (not shown). If the drive motor is switched off—which preferably occurs by switching off the power and deactivating directional switches—to open the cooking chamber or in general to move the base door, a mechanical force and an induction force of the drive motor must be overcome. The force applied to do this must be all the greater the greater the transmission ratio of the drive is. For the embodiment shown a transmission ratio in range of 30:1 to 60:1 has been shown to be a good compromise between self-locking and speed of movement. In particular a transmission ratio ranging from 40:1 to 50:1, specifically of 45:1, is suitable. With a transmission ratio of 45 the base door could not be opened even with a load of more than 20 kg.

One of a number of possible forms of embodiment of the drive is a worm drive. Other types of drive are known to the person skilled in the art of mechanical engineering.

Obviously the transmission ratio is not restricted to this range and can be adapted by the person skilled in the art for example to the specifications of the drive motor used, the mechanical friction of the actuating mechanism of the base door, the type of drive (hoisting cable rope drum etc.), the weight and the loading of the base door and much more besides.

FIG. 9 shows in a side view, similar to that shown in FIG. 4, a view of a further embodiment of the high-level cooking appliance with a more precise description of the drive apparatus from FIGS. 7 and 8. The drive motor 9, the guide housing 54, the fan device 49 and the electronics module 47 are omitted to aid clarity in the diagram. The other side of the cooking device is constructed in a similar way.

The elastically-deformable guide tubes 56 can be seen which rest at the top on the support 57 and are then routed bent downwards into the lifting elements 10. The hoisting cables 58 emerge from the free openings of the guide tubes 56, namely at a section of a hoisting cable 58 bearing a load on this side (left-hand) which is connected via the attachment element 59 to the lower telescopic bar 60 of the lift element 10 and thereby indirectly to the base door 7. The other (right-hand) hoisting cable 58 has a free end on this side. The other hoisting cable 58 is attached or is free respectively on the other side of the cooking appliance. Through actuation of the drive motor the hoisting cables 58, as described above, are displaced linearly and lift the base door 7 up correspondingly or lower it down.

FIG. 10 shows the embodiment of the cooking appliance depicted in FIG. 9 in a sectional view, from the front along the section IV-IV from FIG. 9.

It can be seen that the hoisting cables 58 and the guide tube 56 are diverted at the support 57 from the horizontal into the vertical. On each of the supports 57 a (deflection) force is therefore exerted by the respective load-bearing section of the hoisting cables 58 via the elastically-deformable guide tubes 56 which essentially depends on the load on the load-bearing section of the hoisting cable 58, including the weight of the base door 7 and the load on the door. In this diagram only the normal components Fn1, Fn2 of the respective deflection force are plotted.

By measuring the deflection force, especially the respective normal force Fn1 or Fn2 on the corresponding support 57, an overloading of the base door 7 or an instance of trapping can for example be detected.

The overloading of the base door 7 is for example measurable by a specific load threshold being undershot.

A case of trapping in the closing direction of movement of the base door 7, i.e. mostly between base door 7 and housing, as well as in the opening direction of the base door 7, i.e. at least between a base door 7 and work surface, can for example be detected if a difference between Fn1 and Fn2 becomes greater than a specific set threshold value. Alternately time differences in the relieving of the load between the two sides can be detected.

FIG. 11 shows in greater detail a section depicted by the dashed line circle in FIG. 10.

Here the support 57 moves a switching lever 62 which switches a switch 63 when the load is relieved. In this exemplary embodiment it is only possible to detect a value falling below or exceeding a load threshold value. Possible applications, embodiments and measurement principles are described for this process example in DE 102 28 140 A1 and DE 101 64 239 A1.

Alternately other load-measuring sensors are can be used which measure forces acting on the support 57, especially but not only, the normal force Fn. In these cases further evaluation options for detecting the trapping can be used such as for example a speed change of the load which may exceed a specific threshold value or may deviate from a setpoint value (e.g. a speed of movement or speed ramp) and which indicates the trapping in this way.

FIG. 12 shows, like the diagram depicted in FIG. 7, a further embodiment of the cooking appliance with an emergency opening arrangement for moving the base door in the event of a power outage at the cooking appliance or a failure of the drive motor 9.

The drive motor 9 has a toothed wheel in the form of a beveled wheel 65 at a power take-off 64 which is actively connected to the motor shaft (not shown). In addition a fixed rotatably supported shaft 66 is present on the end of which is a toothed wheel in the form of a beveled wheel 67. The other end of the shaft 66 is embodied and arranged as an override unit or area 69 for operation by the user. The shaft 66 is attached by two brackets 68 to the housing body 34 and in addition has a retaining element 70 in the form of the spring which in normal operation holds the shaft 66 in position with a retaining force Fr (indicated by the arrow), in which the beveled wheel 67 of the shaft is decoupled from the beveled wheel 65 of the drive motor 9. The shaft 66 has a hexagonal cross section so that a control element, embodied as a crank or a hexagonal key for example, is easily able to be placed over the end embodied as the override unit 69 (not shown). In normal operation the end embodied as the override unit 69 is concealed behind the front panel or the front housing cover 35.

In emergency operation when the drive motor 9 can either no longer be actuated via the control panel or the power to the entire appliance has failed, the emergency opening arrangement still allows the base door to be moved. To this end, in this embodiment the front panel is first removed so that the user obtains access to the override unit 69. The user then places a crank with a suitable cutout onto the shaft 66 and pushes the shaft 66 back against the retaining spring force Fr with its beveled wheel 67 into contact with and thereby so that it engages with the beveled wheel 65 of the drive motor 9. By subsequently turning the crank the drive motor 9 and thereby by association the pinion 55 and the hoisting cables are moved, which causes the base door 7 to be moved.

On return to normal operation the pressure is released from the shaft 66, the crank is taken off and the front panel is put back on.

The toothed or beveled wheel 65 can be directly attached to the motor shaft. The shaft 66 can also be flexible. The operating part can be permanently connected to the override unit 69 or the shaft 66. The emergency opening arrangement can also be structured so that the shaft is not decoupled during normal operation and thus turns permanently as well. As well as a shaft any other device is suitable which transfers mechanical forces without power, namely from the override unit 69 or an operating part to the motor shaft.

LIST OF REFERENCE SYMBOLS

1 Housing

2 Wall

3 Cooking chamber

4 Viewing window

5 Muffle

6 Muffle opening

7 Base door

8 Work surface

9 Drive motor

10 Lifting element

11 Control element

12 Control panel

13 Control circuit

14 Display elements

15 Cooking zone

16 Hotplate heating elements

17 Hotplate heating elements

18 Radiant heating elements

19 Glass ceramic plate

20 Holder part

21 Food carrier

22 Overhead heating element

23 Fan

24 Seal

25 Movement control panel

25 a Upwards movement switch

25 b Downwards movement switch

26 Movement control panel

26 a Upwards movement switch

26 b Downwards movement switch

27 Memory unit

28 Actuation button

29 Main switch

30 Motor shaft

31 Retaining element

32 Measuring sensor

33 End switch

34 Housing body

35 Housing cover

36 Space

37 Lower ventilation openings

38 Upper surface of the housing body (34)

39 Upper ventilation opening

40 Space

41 First (inner) viewing window

42 Second (middle) viewing window

43 Third (outer) viewing window

44 Side spaces

45 Front space

45 a First front space

45 b Second front space

46 Rear space

47 Electrical or electronics module

48 Drive apparatus

49 Ventilation device

50 Fan

51 Induction channel

52 Exhaust channel

53 Air outlet

54 Guide housing

55 Toothed wheel

56 Guide tubes

57 Support

58 Hoisting cables

59 Lower telescopic bar

60 Hoisting cable attachment

61 Upper telescopic bar

62 Switching lever

63 Switch

64 Housing power take-off

65 Toothed wheel

66 Shaft

67 Toothed wheel

68 Brackets

69 Override unit

70 Retaining element

Fn1 Normal force 1

Fn2 Normal force 2

Fr Retaining force

P0 Zero position

P1 Intermediate position

P2 Intermediate position

PZ End position 

1-7. (canceled)
 8. A cooking appliance comprising: a cooking chamber; at least one muffle which delimits the cooking chamber; the muffle having a muffle opening; a door for closing the muffle opening; a drive motor for moving the door; a self-locking transmission associated with the drive motor.
 9. The cooking appliance as claimed in claim 8 wherein the self-locking transmission includes a worm transmission.
 10. The cooking appliance as claimed in claim 8 wherein the self-locking transmission has a transmission ratio ranging between 30:1 to 60:1.
 11. The cooking appliance as claimed in claim 10 wherein the self-locking transmission has a transmission ratio ranging between 40:1 and 50:1.
 12. The cooking appliance as claimed in claim 11 wherein the transmission ratio is 45:1.
 13. The cooking appliance as claimed in claim 8 wherein the drive motor is short circuited when the muffle opening is closed by the door.
 14. The cooking appliance as claimed in claim 8 wherein the cooking appliance is a high-level cooking appliance; the muffle opening is a floor-side muffle opening; and the door is a base door. 